The kinetics of cohesive powder de-agglomeration from three inhaler devices

PurposeThe purpose of the current investigation is to understand the kinetics of de-agglomeration (kd) of micronised salbutamol sulphate (SS) and lactohale 300 (LH300) under varying air flow rates (30-180 l min−1) from three dry powder inhaler devices (DPIs), Rotahaler® (RH), Monodose Inhaler® (MI) and Handihaler® (HH).ResultsCumulative fine particle mass vs. time profiles were obtained from the powder concentration, emitted mass and volume percent <5.4 μm, embedded in the particle size distributions of the aerosol at specific times. The rate of de-agglomeration (kd), estimated from non-linear least squares modelling, increased with increasing air flow rates. The kdvs. air flow rate profiles of SS and LH300 were significantly different at high air flow rates. The kd was highest from RH and lowest from MI. Differences in kd between the devices were related to device mode of operation while the differences between the materials were due to the powder bed structure.ConclusionThis approach provided a methodology to measure the rate constant for cohesive powder de-agglomeration following aerosolisation from commercial devices and an initial understanding of the influence of device, air flow rate and material on these rate constants.

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